UCARP allows a pair of hosts to share common virtual IP
addresses in order to provide automatic failover. It is a
portable userland implementation of the secure and patent-
free Common Address Redundancy Protocol (CARP,
OpenBSD's alternative to VRRP). Strong points of the CARP
protocol include its very low overhead, cryptographically
signed messages, interoperability between different
operating systems and no need for any dedicated extra
network link between redundant hosts.
